Process for producing nickel-coated steel



Jan. 9, 1968 N. M. PARIKH ETAL 3,362,833

PROCESS FOR PRODUCING NICKEL-COATED STEEL Filed April 30, 1964 2 Sheets-Sheet l w M m 0 m W mam m 7 r 96% Q o$k0$ m M p o NN g gwkk 1 MM h 2 A K p 090 00000000 WW 0 o @N mqwiQ @SE VN m K WWNWQ B 0 9 N Nw OOQDQOOQ 0 FL Ow United States Patent 3,362,838 PROCESS FOR PRODUCING NICKEL-COATED STEEL Niranjan M. Parikh, Park Woods, and Robert L. Hodson,

Oak Lawn, Ill., assignors, by mesne assignments, to The International Nickel Company, Inc., New York, N.Y.,

a corporation of Delaware Filed Apr. 30, 1964, Ser. No. 363,911 4 Claims. (Cl. 106-162) The present invention is directed to a method for producing relatively thin nickel coatings on steel and, more particularly, to an essentially continuous method for producing thin, dense, very uniform nickel coatings on steel strip using nickel powder as the source of nickel.

For many years it has been recognized that an economical method for producing thin, dense, corrosion resistant nickel coatings upon carbon and low alloy steel shapes such as strip, sheet and the like would be highly desirable in many industrial and consumer applications. Attempts have been made to effect this desirable result. Thus, a common method for applying thin nickel coatings to steel objects comprises the electroplating process. While this process has been used extensively in many applications, it is quite expensive and is not readily applicable to the economic production of nickel-coated steel in the form of long strips, large sheets and the like. Thus, in such instances, the capital investment required to install plants having sulficient capacity to yield a nickel coating about 2 mils thick upon long coils of steel strip or the like is so high that no such commercial installation can be installed with any prospect of recouping the required investment. Other means of applying nickel coatings, including flame spray coatings, are known but these methods also suffer serious disadvantages from the standpoint of cost and further it is difficult to produce thin coatings which are dense and free from pores through the use of such methods. The cladding of heavy steel plate with sheets of nickel, which are applied to the steel by means of welding and/or hot rolling, is also widely employed but such cladded steel plate is not economically produced at thicknesses of less than about /2 inch. It is also possible in connection with heavy plates and other heavy steel shapes to apply a nickel coating by welding methods. However, none of the foregoing methods is successful either from the standpoint of cost or from the standpoint of producing a thin, uniform coating substantially free from pores on thinner steel shapes such as sheet and strip which generally do not exceed about 0.165 inch in thickness. Accordingly, such nickel-coated steel materials are not now available commercially, although there are many industrial applications in which such materials could be usefully employed if they were made available at a suitable cost level.

A method has now been discovered whereby nickel coatings which are thin, dense, free from pores, and very uniform can be economically produced on a substantially continuous basis upon flat cold-rolled steel in a coil form, i.e., materials manufactured to strip and sheet tolerances, using nickel powder as the source of nickel.

It is an object of the present invention to provide a method for producing nickel-coated steel strip or sheet having a nickel coating which is thin, dense, and very uni form.

Another object of the invention is to provide an improved process for producing nickel coatings which are thin, uniform, and substantially free from pores upon long, thin, coilable steel shapes.

A still further object of the invention is to provide sound, substantially pore-free nickel coatings on thin steel shapes.

A further object of the invention is to provide a method for nickel coating carbon and low alloy steel which may be employed in high speed modern steel mill lines with minimum disruption of the production scheme.

It is another object of the invention to provide an economical method for producing thin steel strip in coil form having a dense, protective nickel coating derived from a primary form of nickel.

Other objects and advantages of the invention will be made evident from the following description and the accompanying drawing in which:

FIGURE 1 is a representation of a method whereby a thin nickel coating is applied to coil steel strip;

FIGURE 2 is a modification of the representation set forth in FIGURE 1 wherein additional compaction steps are employed;

FIGURE 3 is a further modification of the modified method depicted in FIGURE 2;

FIGURE 4 is a representation depicting a method in accordance with the invention for coating coiled steel strip on both sides thereof wherein steel strip is transported vertically during the coating operations; and

FIGURE 5 depicts a modification of the methods illustrated in FIGURE 4 wherein additional compaction operations are employed before and after sintering of the nickel coating.

Broadly stated, the present invention comprises a method for producing a thin, dense nickel coating upon a thin, flat, coilable, strip-like steel shape having substantial length with respect to its width wherein at least one surface of the steel shape is treated to remove therefrom any rolled-in oxides and/or other surface imperfections; the thus-treated steel surface is then coated with an alkaline slurry containing about 50% to about by weight, of fine (i.e., less than about 10 microns average particle size) nickel powder, a small quantity, e.g., about 0.1% to about 5%, by weight, of a volatilizable organic binder or film former, a Wetting agent, and a volatilizable vehicle; the thus-applied coating is then dried to remove the vehicle from the slurry coating; and the dried coating is then sintered in an atmosphere nonoxidizing to steel at a temperature of about 1300" F. to about 2200 F. or 2300 F., e'.g., about 1800" F. to about 2100" F., for a time of about 15 seconds to about minutes, e.g., about 20 seconds to about 10 minutes (with the shorter times being employed at the higher temperatures), to produce a sintered coating bonded to the steel and having suflicient adhesive and cohesive integrity that the strip-like steel shape at this point can be coiled. In order to effect the final compacting of the sintered nickel coating and to provide a finished nickelcoated flat steel strip-like shape, the sinter-coated steel is then subjected to one or more rolling operations and one or more annealing operations to provide the final product having a thickness range of generally about 0.015 to about 0.165 inch, having a dense, thin, strongly adherent nickel coating substantially free from pores, and having a nickel thickness generally in the range of about 0.5 to about 10 mils depending upon the initial thickness of nickel applied and the amount of cold reduction applied to the steel in the production scheme. Generally, the nickel coating provided in accordance with the invention will be about 2% to about 20% of the thickness of the nickel-coated article.

A slurry composition which is particularly useful for roller coating application to steel to produce uniform coatings comprises, on the basis of about parts, by weight, of slurry, about 71 to about 75 parts, by weight, of fine nickel powder having an average particle size of about 2 to 5 microns, about 29 parts, by volume, of methyl cellulose as a 1% aqueous solution, a small amount of a wetting agent to provide in the liquid portion of the slurry a surface tension of about 30 to 50 dynes per centimeter, with the slurry having a pH of not lower than about 8. It is to be understood, however, that the composition of the slurry and the viscosity thereof can be varied widely depending upon the coating technique to be employed. As will readily be understood, the viscosity of the slurry is reduced by reducing the quantity of nickel powder employed therein to amounts as low as about 50 parts, by weight, and conversely, the viscosity of the slurry can be increased by increasing the quantity of nickel powder employed therein to amounts as high as about 80 parts, by weight. The viscosity of the slurry may also be increased by increasing the amount of organic binder or film former employed. Thinner, i.e., less viscous, slurries can be applied to the prepared steel strip surface by spraying and thicker, i.e., more viscous, slurries, can be applied to the steel strip by a doctor blade technique. In general, slurries containing greater amounts of nickel provide thicker nickel coatings on the steel. In compounding the slurry, it is advantageous to subject the slurry to thorough mixing and permit it to stand for some time, e.g., several hours, to permit escape of entrapped air bubbles. The use of a wetting agent in the slurry is important and an amount of wetting agent is employed to decrease the surface tension of the slurry. Such agents also afford a measure of viscosity control in the slurry, facilitate adherence of the slurry to the steel strip, contribute a desirable leveling action to the slurry coating on the steel, and provide an improvement in the integrity of the final dense nickel coating. it is also important to control the pH of the slurry such that it is not lower than about 8 in order to prevent rusting of the steel during the time between application of the slurry mixture thereto and the completion of the drying operation. A source of hydroxyl ion is added to the slurry for this purpose. The hydroxyl ion source advantageously is ammonia or ammonium hydroxide, although other nitrogen bases such as the primary, secondary, tertiary and quaternary amines and other common reagents providing a basic reaction such as sodium hydroxide, sodium carbonate, potassium hydroxide, potassium carbonate, etc., may also be employed. It is quite important to prevent rusting of the steel strip since it has been found that when rust is present or has formed on the steel before the sintering operation it will contribute to the formation of pits and/or other types of undesirable discontinuities in the final nickel coating. It is also to be understood that heat-decomposable or volatilizable polymeric binders or film formers other than methyl cellulose which thicken water, which exert a stabilizing, dispersing, and anti-settling effect in the slurry, and which also yield low ash upon decomposition during the sinter ing operation may be employed in the slurry. Polyvinyl alcohol, starch, modified starch, chemically derivatized starch such as ethoxylated starch, cyanoethylated starch, etc., are examples of such materials. Binders or film formers assist in providing uniform initial nickel coatings on the steel and contribute green strength to the dried coating. Methyl cellulose is a very satisfactory binder from the standpoint of cost and efficacy and it is operable in an aqueous slurry containing nickel powder. The binder materials are of such a chemical nature that relatively small amounts in the vehicle, e.g., water, will provide a workable viscosity. For example, in the case of methyl cellulose, a proper viscosity for an aqueous roller coating slurry is obtained by employing about 0.15% to about 1%, by weight, of methyl cellulose in the slurry. The wetting agent, which can be of the nonionic, anionic or cationic type, and can be, for example, dioctyl sodium sulfosuccinate (sold under the trademark Aerosol OT), ethylene oxide condensation products of the primary fatty acids (sold under the trademark Ethomeen C-15), phosphorated higher alcohols (sold under the trademark Victawet 58-13), aliphatic substituted butyne diols and octyndiols (sold under the trademarks Surfynol 82 and Surfynol 104 E), dihexyl ester of sodium sulfosuccinic acid (sold under the trademark Aerosol MA), etc., is

added to the other liquid ingredients of the slurry in an amount to control the surface tension of the liquid ingredients to the range of about 30 to about 50 dynes per centimeter. If it is found that the slurry exhibits undesirable foaming tendencies, a small addition of an anti-foaming, or defoaming agent such as 2-octanol, a sulfonated oil or a silicone is made to the slurry to correct the condition. It is advantageous from many standpoints, including that of process economy, to employ an aqueous slurry although the use of nonaqueous media (vehicles) in the slurry are also contemplated within the scope of the invention. Thus, various organic solvents can be employed as vehicles in the slurry for the purpose of dissolving or dispersing the film former or binder employed therein. Satisfactory vehicles include various alcohols, including methanol, ethanol, propanol, butanol, furfuryl alcohol, benzyl alcohol, etc., ketones, including methyl ethyl ketone, acetone, methyl isobutyl ketone, etc., formamide, dimethyl formamide, ethylene glycol, etc.

The drying operation can be conveniently carried out by means of gas-fired infrared heaters. It is also to be understood that satisfactory atmospheres which may be employed during the first sintering operation may comprise atmospheres derived from cracked ammonia, dry hydrogen and the like.

It is contemplated that the invention will be particularly applicable in conventional steel mill practice at the hot band stage of steel strip manufacture. At this point in the steel mill production scheme, the steel strip commonly has a thickness in the range of about 0.05 inch to about 0.25 inch and is readily coilable. Hence, coils of hot-rolled steel strip can be removed from the circuit, can be appropriately surface treated and coated with the nickel-sinter coating described hereinbefore, and can then be returned to the regular mill production scheme for finishing by cold rolling and annealing to provide nickel-coated steel strip having the desired thickness and having a dense nickel coating about 0.5 to 10 mils thick essentially free from pores.

For the purpose of illustrating the application of the invention to the nickel coating of steel mill hot bands, reference is now made to the accompanying drawing. In the drawing, FIGURE 1 depicts schematically one embodiment of a method whereby steel mill hot bands are coated with a nickel-sinter coat in accordance with the invention and are thus prepared for return to the steel mill production scheme at the hot band stage. In the drawing, 11 depicts a payoff machine holding coils of descaled steel strip, e.g., pickled hot bands, 12 and 13 which pass to a welder 14 adapted for the purpose of welding ends of the hot band coils together. The strip can then pass through a looper or looping pit to obtain constant speed in the line. A leveler 16 adapted to correct minor shape irregularities in the steel hot bands desirably is employed. The hot band is subjected to treatment in an abrading machine as depicted at 17 to remove from at least one side of the steel strip minor discontinuities, oxides, mill defects, etc. Feeder rolls 18 can be disposed between the various machines. A slurry blending tank 19 can be emplayed to mix aqueous nickel powder slurry which is fed to roller coater device 20 adapted to coat at least one side of the steel hot band being treated with an aqueous slurry containing nickel powder and having the composition set forth hereinbefore. The coated band is then dried and this can be accomplished in dryer 21 which advantageously comprises a series of infrared gas burners operated at a surface temperature of about 1400 F. and adapted to raise the temperature of the slurry-coated steel strip to about 200 F. as the slurry-coated strip passes through the dryer. After drying, the coated strip is subjected to the sintering operation which can be carried out in sintering furnace 22 having an atmosphere generated by the cracking of ammonia and operated at a temperature of about 2000 F. In the embodiment depicted, the

entire line is operated at such a speed that the steel strip passes through the hot zone of the sintering furnace in about 30 seconds. The sinter-coated steel strip can be coiled after passing through the sintering furnace 22, for example, upon coiler 23. The nickel coating on the coil at this point of the process is still quite porous but is well bonded together and to the basis steel strip. No appreciable cracking is found in the coating. Coils of strip prepared in this fashion may be returned to the steel mill circuit and finished through the final cold rolling mills and annealing furnaces employed in producing cold-rolled sheet and strip. If desired, the nickel coating line may be modified as depicted in FIGURES 2 and 3. In the modification of FIGURE 2, the steel strip bearing the dried nickel powder coating is passed through floating rolls 24 and/or pinch compaction rolls 25 to increase the density of the nickel coating at this point from approximately 50% to approximately 80% of theoretical density. As a further modification depicted in FIGURE 2, compaction rolls 26 may be inserted in the cooling zone of the sintering furnace at a point where the ambient temperature is about 800 F. to about 1900 F. to effect further compaction of the sintered coating up to about 90% of coating theoretical density prior to coiling. Alternatively, as depicted in FIG- URE 3, one or more sets of compaction rolls 27 may be inserted in the line directly beyond the sintering furnace to effect cold compaction of the sintered coating prior to coiling of the strip.

FIGURE 4 depicts one further modification of the process particularly adapted for coating both sides of steel hot bands wherein the strip is caused to pass in a vertical direction from the abrading operation 17 through the coating, drying, and sintering operations 20, 21, and 22, respectively, to the rewind coiler 23. It will be appreciated that in this way the surfaces of the steel strip do not touch the working apparatus until after the sintered nickel coating is applied therto. FIGURE 5 depicts a further modification of FIGURE 4 wherein pinch rolls 25 are inserted between the drying and sintering operations and wherein hot compaction rolls 26 are inserted in the cooling zone of the sintering furnace in order to provide nickel coatings which are substantially 90% to 95% of theoretical density as a part of the nickel coating operation.

In order to give those skilled in the art a better understanding of the invention, the following illustrative examples are given:

EXAMPLE I The production of a low carbon steel strip 0.035-inch thick and having a two-mil thick nickel coating in accordance with the invention will now be described. Steel hot bands 0.083-inch thick were surface ground to clean the surface thereof. It will also be understood that chemical or electrochemical pickling or a combination of pickling and grinding, etc., is also satisfactory for this purpose. An aqueous slurry containing about 71 to 75 grams of carbonyl nickel powder having a particle size in the range of 2 to 5 microns, about 29 milliliters (ml.) of methyl cellulose as a 1% aqueous solution, about 3 ml. of a solution of dioctyl sodium sulfosuccinate (sold commercially under the trademark Aerosol OT) as a wetting agent, and about 1 ml. of ammonium hydroxide solution (9N) for pH control was prepared. This slurry was applied by roller coating to the cleaned surface of the steel hot bands. The coated strip was then dried in an infrared drying line and it was found that the density of the dried coating was about 50%. The strip was then sintered in a temperature range of about 1900" F. to about 2100 F. for a time period of about 20 to 30 seconds in a protective atmosphere comprising the products obtained by cracking ammonia. At this point, it was found that the strip could be bent easily around a /2-inch diameter rod without cracking of the nickel coating. The coating on the sinter-coated strip was then consolidated in a rolling mill to reduce the total thickness thereof from about 0.090 inch to about 0.082 inch to develop in the coating a density of about to about of theoretical and to maintain a minimum reduction in the steel, i.e., not more than about 2% reduction. The consolidated coated strip was then annealed at 1600 F. for about 30 minutes in a protective atmosphere. It was found that this anneal rescrystallized the nickel of the coating and developed a steel-nickel diffusion zone which was about 10% to about 15% of the thickness of the nickel coating. It is to be understood that the anneal employed at this point can be conducted over a wide temperature range such as about 1300 F. to about 2000 F. for a period of time of about 20 seconds to several hours depending on the nickel coating thickness at this stage with the shorter times being employed at the higher temperatures. The strip was then cold rolled in two passes to a thickness of 0.050 inch thereby developing full density in the coating. It was then reannealed at about 1400 F. for about 15 minutes so as to recrystallize the steel and the nickel. The strip was then cold rolled to the final 0.035-inch thickness in one pass and annealed again at 1400 F. to recrystallize the steel and the nickel without substantially affecting the diffusion zone. The steel strip was found to have a fully dense nickel coating with a thickness of about 2 mils. The coating passed the hot water test for 6 hours and the salt spray test (5% solution NaCl) for 96 hours without exhibiting rust in either test. Both flat panels and bent specimens were employed in the salt spray tests. It will be appreciated that in usual steel mill processing cycles the sinter-coated steel is rolled to final gage in the cold rolling stands and is then annealed. If desired, a final skin-pass or temperpass may be given to the steel coil and it is then ready for shipment.

EXAMPLE II A low carbon cold-rolled and annealed steel strip material about 0.075-inch thick was employed as a starting substrate. The steel stock was degreased and was then roller coated with an aqueous slurry composition containing in weight percent about 75% fine carbonyl nickel powder, about 1% of a solution containing 2.5% of dioctyl sodium sulfosuccinate, about 0.25% of ammonium hydroxide stock solution containing about 29% NH by weight, and the balance 1% aqueous solution of methyl cellulose. The resulting coated strip was dried and sintered at about 2000 F. in a hydrogen atmosphere to provide a sinter coating about 16 mils thick and having a theoretical density of about 50%. The sinter-coated strip was lightly rolled to consolidate the coating, was annealed at about 1600 F. for about 30 minutes in hydrogen, was cold rolled about 40%, was again annealed at 1400" F. for 15 minutes, was rerolled to a 0.028- inch thickness, and reannealed at about 1400 F. for 15 minutes. The nickel coating was fully dense and was about 2 mils thick. Panels from the nickel-coated material were hand buffed to a lustrous finish and others were buffed to a fine scratch pattern. The panels were electroplated with 10 microinches of standard decorative chromium to provide a group of panels having a mirror finish and a group of panels having a brushed chromium finish. Representative panels from each group were subject to a deforming operation between rolls to provide rolled-in beads having a i -inch radius in the panels. Parallel beads were rolled to provide a tension bead and a compression bead in the coating and an additional bead of the same dimension was then rolled across each of these panels at right angles to the original beads such that the effects of a double draw and a reverse draw were created in the initial tension and compression beads, respectively. Flat panels and deformed panels from each group were subjected to the accelerated corrosion test designated ASTM B 368-6lT-Copper Accelerated Acetic Acid Salt Spray Test (CASS test) for a period of 22 hours. Panels were then rated in accordance with the method established by ASTM Committee B8. The majority of panels had a rating of 9 or 10, i.e., less than 9% of the panels exhibited rust indications that were greater than 0.1% of the area exposed to the corrosive solution. The deformed panels behaved in the same fashion as the fiat panels, i.e., the few rust indications were at random locations and not at any particular bead indentation or junction of beads, thus demonstrating the protective value of this ductile coating.

It is to be understood that the use of the wetting agent in the initial slurry mixture is a very important step from the standpoint of avoiding pores in the final nickel coating. Proper pH control, as exemplified by the use of a small ammonia addition to insure an alkaline state in the initial slurry mixture is also important for the same reason. Ammonia is a most attractive compound for the purpose of pH control because it is highly effective, leaves no ash, and is quite inexpensive. It is also to be understood that roll comp-action of the sintered nickel coating is essential in order to provide the final fully dense nickel coating contemplated in acordance With the invention. It has been found that if any of the aforementioned important ingredients or controls is omitted from the initial slurry, much less satisfactory results are obtained in the final nickel coating and the incidence of defects in the final coating is increased.

The special process contemplated in accordance with the invention wherein both a wetting agent and an agent for effecting pH control is employed in the initial slurry yields a final nickel-coated steel strip having essentially no defects in thee oating as revealed by the hot water porosity test. This test has been found to be a very searching test for defects in thin nickel coatings on steel and comprises immersing specimens in continuously aerated pure water maintained at a minimum temperature of 185 F. for 1 to 6 hours, depending upon the coating thickness with longer times being used for thicker coatings.

It is highly advantageous in accordance with the invention to employ fine carbonyl nickel powder having a particle size in the range of about 2 to 5 microns. it appears such high purity powders are uniquely applicable in the process, especially when the roller coating technique is employed in initially applying the nickel-containing slurry to the prepared steel strip. It is contemplated that coarser nickel powders having lower purity than carbonyl nickel powder might be employed but it is then necessary to employ higher sintering temperatures, longer sintering times, and greater amounts of reduction in the rolling operations in order to obtain the required high density and freedom from porosity in the final nickel coating contemplated in accordance with the invention. It is also contemplated and, in some instances, it is quite desirable to replace up to about 65% or about 75% by weight of the initial nickel powder with copper powder. in such instances, nickel-copper alloy coatings are produced which are advantageous in certain environments.

It will be appreciated that the process contemplated in accordance with the invention can be carried out either in a continuous or a semicontinuous fashion. The sintercoated strip has sulficient integrity to be coiled. Accordingly, the further compacting and annealing steps employed as described hereinbefore to produce the final nickel-coated strip having 100% of theoretical density can be carried out either batchwise or in a continuous line. In many installations, it is advantageous to carry out the rolling and annealing operations in batches. Thus, conventional batch-type furnaces in which coils of strip can be stacked, and a protective atmosphere maintained therein during the annealing operation, may be employed. Advantageously, the open-coil annealing system is employed as otherwise steps must be taken to prevent sticking of the coil faces.

The final product in accordance with the invention can be welded, drawn, or formed without losing the protective character of the nickel coating. Nickel-coated articles stamped or otherwise formed from nickel-coated steel produced in accordance with the invention can be coated with chromium for decorative purposes as by electrodeposition or otherwise.

Although the present invention has been described in conjunction with preferred embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the invention and appended claims.

We claim:

1. An alkaline slurry composition containing about 50% to about 80%, by weight, of metal powder consisting of, on the basis of metal powder weight, up to about of copper powder and the balance essentially nickel powder having a particle size not exceeding about 10 microns, a water-dispersible polymeric binder, a wetting agent, and the balance essentially water.

2. A nickel-containing slurry composition particularly applicable to the coating of steel which has a pH not lower than about 8 and contains, by weight, about 50% to about carbonyl nickel powder having a particle size of less than about 10 microns, a binder from the group consisting of methyl cellulose, polyvinyl alcohol, starch, modified starch and chemically derivatized starch, a wetting agent to provide a surface tension of about 30 to about 50 dynes per centimeter in the liquid onstituents of the slurry, and the balance essentially water.

3. A slurry composition according to claim 2 containing about 0.1% to about 5%, by weight, of binder.

4. A nickel-containing slurry composition particularly applicable to the coating of steel which consists essentially of about 71 to about 75 parts, by weight, of car bonyl nickel powder having a particle size of about 5 to about 8 microns, about 29 parts, by volume, of methyl cellulose as a 1% aqueous solution, a small amount of a Wetting agent to provide in the liquid portion of the slurry a surface tension of about 30 to 50 dynes per centimeter, about 1 part, by volume, of ammonium hydroxide, and the balance essentially water.

References Cited UNITED STATES PATENTS 1,922,254 8/ 1933 McCulloch 117-46 2,289,614 7/1942 Wesley et al. 117-46 2,681,375 6/1954 Vogt I 75222 2,698,810 1/ 1955 tauffer 11722 2,836,641 5/1958 Vogt 11 75222 3,142,560 7/1964 Storchheim 117-22 3,186,871 6/1965 Donohue 75208 3,197,847 8/1965 Kerstetter 75-208 3,216,845 11/1965 Brown 117-35 3,246,995 4/1966 Moore 106-1 FOREIGN PATENTS 598,653 2/1948 Great Britain.

RICHARD J. HERBST, Primary Examiner.

A. L. HAVIS, Assistant Examiner. 

1. AN ALKALINE SLURRY COMPOSITION CONTAINING ABOUT 50% TO ABOUT 80%, BY WEIGHT, OF METAL POWDER CONSISTING OF, ON THE BASIS OF METAL POWDER WEIGHT, UP TO ABOUT 75% OF COPPER POWDER AND THE BALANCE ESSENTIALLY NICKEL POWDER HAVING A PARTICLE SIZE NOT EXCEEDING ABOUT 10 MICRONS, A WATER-DISPERSIBLE POLYMERIC BINDER, A WETTING AGENT, AND THE BALANCE ESSENTIALLY WATER. 